We propose to conduct a methodological study designed to assess the authenticity of human toenail specimens a multi-element monitor. The toenail monitor has been demonstrated to accurately differentiate selenium intake and also occupational exposure of cadmium. The first objective of this study is to expand its utilization to as many other trace-elements as feasible. The major question to be answered at this point is: to what extent are toenails contaminated from the cutters and to a lesser extent by use of nail polish? Furthermore, how can this contamination be removed or managed? The second objective is to apply the new methodology to approximately 800 toenail specimens already collected in two case-control health studies addressing primarily breast and lung cancer and cardiovascular heart disease (CHD). The contamination study will employ neutron activation analysis (NAA) to profile the potential sources, i.e. the cutters and nail polishes. There are three common materials from which nail cutters are constructed and two different styles; stainless steel and chromium- and nickel-plated steel, and scissors and clippers. All six combinations will be analyzed. A selection of nail polishes which is representative of available colors will also be analyzed by NAA. These data will be used to determine specific activities and ratio of contaminants. The cutters will be irradiated to produce radioactive tracers which will be transferred to plastic sheets having Mohr hardness values which bracket the average value for human nails, 2.5. Using this radiotracer approach, as little as 2 x 10-10g of cutter transferred can be detected. A similar approach will be used for nail polishes. From these experiments, we expect to learn how to identify contaminated specimens and work toward decontamination solutions. Two aspects of the contamination study will be carried over to the application study, i.e. the cleaning procedures and the identification of elemental profile. This information will be used to establish the most comprehensive trace-element profile possible for application to the 800 specimens collected in the Breast Cancer Trial of the Nurses' Health Study (NHS) and the South Dakota Regional Health Study (SDRHS). In both of these studies, our ultimate goal is to seek correlations between trace- element nutrition and the occurrence of cancer and CHD. These epidemiological analyses will be done by Dr. Walter Willett's Group at Harvard University, School of Public Health and are not a part of this proposal.